Technical Field
The present invention relates to an information recording medium in which predetermined information is recorded by irradiation of laser light and made readable in infrared light, while being made invisible externally in visible light. Particularly, the present invention relates to an information recording medium which is suitably used in a card game apparatus configured to advance a game by reading card data recorded in cards.
Related Art
In recent years, there have been card game apparatuses configured to advance a game by reading data recorded in cards. In such a card game apparatus, a player purchases game cards, and arranges these cards on a card arrangement panel of the card game apparatus, and the card game apparatus then reads card data recorded on the back surfaces of the cards by an image sensor in the apparatus, so that a game can be advanced.
For example, JP 2007-029757 A discloses a card to be used in a card game apparatus as described above.
In JP 2007-029757 A, an image, picture pattern or photograph that displays a game character is visibly printed on one surface of the card, and on the other surface of the card, information related to the game character is printed as a two-dimensional code pattern. The code pattern is formed in such a manner as to be discernable by an optical reading unit using an infrared ray, and further, a coating permeable to an infrared ray is applied to the surface of the code pattern to make the code pattern invisible externally, so that information on the card is hidden.
As a method for forming a code pattern on a card as described in JP 2007-029757 A, a printing method such as offset printing is commonly used. However, in the printing method such as offset printing, the number of code patterns that can be formed with one printing plate is limited, and therefore for increasing the number of code patterns, a large number of printing plates must be provided, so that game functions are inevitably limited. Accordingly, the demand for cards in which a specific code pattern can be arbitrarily formed for each card is increasing.
In this connection, a method for arbitrarily forming a specific code pattern for each card may be an inkjet method. In the inkjet method, an arbitrary code pattern can be formed on a card, but for hiding the code pattern so that it cannot be viewed, it is necessary to shield the code pattern by printing a picture pattern thereon after forming the code pattern. The code pattern cannot be discriminated after it is shielded, and therefore stock control is complicated and time-consuming.
Recently, printer-mounted card game apparatuses have been becoming trendy, and for the printer-mounted card game apparatuses, it is desired to print a card design on demand at the time of issuing a card, and also to form a specific code pattern for each card.
Under these situations, JPH 11-235871 A proposes an infrared ray absorbing marking forming article as a medium which is hardly recognizable in a visible light ray and which is recognizable in an infrared ray. The infrared ray absorbing marking forming article includes a substrate which at least partially includes a layer containing a visible light ray non-absorbing and infrared ray absorbing material, or a substrate which contains a visible light ray non-absorbing and infrared ray absorbing material, the infrared ray absorbing material having a characteristic in which infrared ray absorbance is at least partially lost by external energy.
According to the technique proposed in JPH 11-235871 A, predetermined information can be recorded in a medium such as a card by laser light, and the information recorded in the medium is invisible externally, but can be recognized in an infrared ray, so that complication of stock control when code patterns are formed on cards by an inkjet method as described above can be eliminated.